Since we just finished up learning about North Carolina’s Geologic History, I thought it would be useful to go over everything and make a good study sheet for the next test. Each belt has its age and what is commonly found there:
Blue Ridge Belt
This mountainous region is composed of rocks from over one billion to about one-half billion years old. This complex mixture of igneous, sedimentary and metamorphic rock has repeatedly been squeezed, fractured, faulted and twisted into folds. Close to Boone, NC, Grandfather Mountain Window was formed when younger rocks eroded exposing older rocks below. The Blue Ridge belt is well known for its deposits of feldspar, mica and quartz-basic materials used in the ceramic, paint and electronic industries. Olivine is mined for use as refactory and foundry molding sand.
The Inner Piedmont belt is the most intensely deformed and metamorphosed segment of the Piedmont. The metamorphic rocks range from 500 to 750 million years in age. They include gneiss and schist that have been intruded by younger granitic rocks. The northeast-trending Brevard fault zone forms much of the boundary between the Blue Ridge and Inner Piedmont belts. Although this zone of strongly deformed rocks is one of the major structural features in the southern Appalachians, its origin is poorly understood. Crushed stone for aggregate and building construction is the principal commodity produced.
The belt consists of moderately deformed and metamorphosed volcanic and sedimentary rocks. The rocks are about 400-500 million years old. Lithium deposits here provided raw materials for chemical compunds, ceramics, glass, greases, batteries and televison glasses.
This belt consists of gneiss, schist and metamorphosed intrusive rocks. The principle mineral resource is crushed stone for road aggregate and for building construction.
This belt consists mostly of igneous rocks such as granite, diorite and gabbro. These are 300-500 million years old. The igneous rocks are good sources for crushed and dimension stone for road aggregate and buildings.
This belt consists of heated and deformed volcanic sedimentary rocks. It was the site of oceanic valcanic islands about 550-650 million years ago. This belt is known for its numerous abandoned gold mines and prospects. North Carolina led the nation in gold production before the California Gold Rush of 1849. In recent decades, only minor gold mining has taken place, but mining companies continue to show intereste in this area. Mineral production is crushed stone for road aggregate and pyrophyllite for refractories, ceramics, filler, paint and insecticide carriers.
The basins are filled with sedimentary rocks that formed about 200-190 million years ago. Streams carried mud, silt, sand and gravel from adjacent highlands into rift valleys similar to those of Africa today. The mudstones are mined and processed to make brick, sewer pipe, structural tile and drain tile.
The Raleigh belt contains granite, gneiss and schist. In the 19th century, there were a number of smaRll building stone quarries in this region, but today the main mineral product is crushed stone for construction and road aggregate.
This belt contains slightly metamorphosed volcanic and sedimentary rocks similar to those of the Carolin slate belt. The rocks are poorly exposed and partly covered by Coastal Plain sediments. The metamorphic rocks, 500-600 million years old, are intruded by younger, approximately 300 million year old, granite bodies. Gold was once mined in the belt, and small occurrences of molybdenite, an ore of molybdenum, have been prospected here. Crushed stone, clay, sand and gravel are currently mined in the belt.
The Coastal Plain is a wedge of mostly marine sedimentary rocks that gradually thickens to the east. The Coastal Plain is the largest geologic belt in the state, covering about fourty-five percent of the state’s land area. In the Coastal Plain, geology is best understood from studying data gathered from well drilling. The state’s most important mineral resource in terms of dollar value is phosphate, an important fertilizer component, mined near the coast at Aurora, Beufort County.